1. Field of the Invention
This invention relates to filtering of liquids from gaseous streams, and more particularly to air-oil separators such as those used to remove suspended oil in compressor air discharge systems.
2. Description of the Prior Art
Gas-liquid separators are used in various applications, but are most notably used to separate oil from air. Air-oil separators are typically used where it is necessary to remove suspended oil mist from an air stream, such as in the air discharge systems of air compressors, vacuum compressors and refrigerant compressors. The separator allows the discharged air to be used without the contamination of the oil which has entered the air in the compressor, and provides for the recovery of the oil so that it can be reused. The air-oil separator is typically mounted in a housing or tank having a separation chamber through which the air flows above an oil reservoir. The separator includes coalescing media through which the discharge air passes while the oil is separated from the air flow. The coalescing media is cylindrically shaped and is typically mounted vertically, that is, in which the axis of the cylindrical coalescing media extends in a vertical direction. A shroud may be provided within the separation chamber around the separator to slow the air flow and provide a vertical direction to the air flow as it encounters the separator. The contaminated air usually enters the separation chamber from outside the air-oil separator and flows into the center of the separator where it then flows axially out of the separation chamber. As the air flows radially through the layers of the separator, the oil coalesces and collects in the interior of the separator where it can be syphoned off or drained into the reservoir, typically by means of a scavenging system, so that it can be reused. The flow directions may also be reversed in which contaminated air is introduced into the center of the air-oil separator and flows radially outwardly through the separator with the oil coalescing and collecting on the outside of the separator where it drains into a reservoir. An example of a prior art air-oil separator is shown in U.S. Pat. No. 4,878,929.
The characteristics of the air flow and the size of the separator are limited by the cylindrical configuration of the separator. For example, where the air flows from the outside of the separator into the separator and a shroud is used around the separator in the separation chamber, the air must flow through the narrow annular chamber between the shroud and the outside of the separator before it enters the separator. This annular chamber has a constant cross section, but the air volume decreases through this chamber since some of the air enters the separator, and thus the air velocity decreases toward the top of the separator. Since sufficient clearance must be provided between the shroud and the outside of the separator, particularly at the bottom of this annular chamber, the size of the separator, and thus the effective surface area provided by the separator, is limited by the size of the shroud.
The present invention provides advantages over the prior art designs of air-oil separators that have not been realized heretofore. The present invention provides an air-oil separator which is generally conically shaped, providing a greater effective surface area over the same axial length than the prior art cylindrically shaped separators, since the generally conically shaped separator can be made with a larger diameter at the upper end while still providing sufficient clearance from the shroud at the lower end.
The air-oil separator of the present invention also provides a funnel type action to direct the flow of scavanged oil into a pool or reservoir where the oil can be more easily collected. This feature may be particularly advantageous when the separator is mounted in a horizontal orientation, that is, in which the axis of the separator extends horizontally. In this configuration, the prior art cylindrical separator collected oil along the bottom portion of the separator, and, since the separator extended horizontally, the oil tended to accumulate in this portion of the separator and not readily to drain off. Because the generally conically shaped separator of the present invention has a sloped bottom surface when mounted horizontally, the oil more readily drains from the separator and does not tend to collect in the bottom portion of the separator and inhibit separator performance. As a result, the separator has a longer life because it is not contaminated with accumulated oil.
The generally conically shaped air-oil separators of the present invention may be used in existing oil reservoir tank designs, thus eliminating the need for modification. They may also be used in an inventive new oil tank design which utilizes the advantages of the generally conically shaped separators.
These and other advantages are provided by the present invention of a liquid reservoir tank including a gas-liquid separator, comprising a tank body having an open end, a portion of the tank body forming a liquid separation chamber, another portion of the tank body forming a liquid reservoir; a tank cover covering the open end of the tank body, the tank body and the tank cover providing a gas inlet and a gas outlet with a gas flow through the separation chamber from the gas inlet to the gas outlet; and a gas-liquid separator mounted in the separation chamber in the gas flow between the gas inlet and the gas outlet, the separator comprising a coalescing stage layer and a drain stage layer arranged radially symmetrically about an axis extending through the interior of the separator, one of the layers positioned within the other of the layers, the coalescing stage layer being upstream of the drain stage layer, each of the layers being generally frusto-conical in shape whereby both of the layers are closer to the axis at one end than at the other end.